The Total Specific Dynamic Action of High-Protein and High-Carbohydrate Diets on Human Subjects

Abstract

The specific dynamic action of 2 diets containing 7 and 37% of protein calories was measured for 6 young men in each case, for periods of 6 to 7 hours post prandium, both in a comfortable and in a cool room. The rate of accumulation of extra heat above the fasting sitting metabolism after meals containing about 1000 cal. was found to follow a sigmoid course, the accelerating phase terminating at about 1.5 hours post prandium for the high-carbohydrate (low-protein) meals, and at about 2 to 2.5 hours post prandium for the high-protein meals. Thereafter, the rate of accumulation of extra calories followed the equation expressing the law of diminishing returns. From equations of the latter type fitted to the experimental data, pooled for the 2 environments, the total S.D.A. was calculated, the results being 169 cal. for the high-protein meals and 103 cal. for the high-carbohydrate meals, or 17.0 and 9.6%, respectively, of the total calories consumed. From these equations the hourly rate of extra calorie production was estimated on the basis of the corresponding differential equations. Comparing these rates with even the lightest types of muscular activity of men, it is evident that the S.D.A. of food is an inconsiderable item in the energy metabolism of active men, and in particular that high-protein meals as compared with low-protein meals exert an inappreciable effect in enhancing the thermal load of men working in a hot environment, or in protecting men against a cold environment.